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Proportional Representation by the Single Transferable Vote (STV)
This is a ‘proportional’ electoral system (i.e. PR): it seeks to provide a fair
representation in parliament for all parties contesting the election roughly in
proportion to the votes they win. This means that smaller parties have a chance of
winning some seats.
Parliamentary constituencies
In Ireland TDs are elected in parliamentary constituencies. The number and size of
these constituencies are determined by Constituency Commissions appointed every
few years, which are required to ensure that the number of TDs to the population is
kept within the constitutional limits of between 20,000 and 30,000 per TD, to ensure
that this ratio of TDs to population is basically uniform throughout the country, and to
try and keep constituencies within county boundaries ‘as far as practicable’.
As in all PR systems, the Golden Rule is that the greater the number of TDs elected in
each constituency (referred to as the ‘district magnitude’) the more proportional the
election result. This is because it’s easier to divide seats proportionally when there are
a lot of them.1 Under the Constitution (a.16.2.6), constituencies must elect at least
three TDs, but there is no upper limit on constituency size. In earlier elections
constituencies elected as many as nine TDs, but in recent elections an upper limit has
been set at five TDs (which is the limit set by the 1997 Electoral Act).
In the 2011 election, the country was divided up into 43 constituencies each electing 3
(in 17 constituencies), 4 (in 15 constituencies), or 5 (in 11 constituencies) TDs. Given
the relatively small ‘district magnitude’ of Ireland’s constituencies (by international
standards), this means that the results are a lot less proportional than they might
otherwise be.
How voting occurs in this system
Electoral systems vary in terms of whether the vote is (1) for a candidate or a party,
and also (2) regarding how much choice is given to voters on the ballot paper. In the
case of STV, the vote is for a candidate. The particularly noteworthy feature of STV
is the amount of choice given to voters, who are invited to rank-order the candidates
(1, 2, 3, etc.): voters have the possibility of rank-ordering as few or as many
candidates on the ballot paper as they wish; this includes being able to vote for
candidates from as many of the parties as they wish. A sample of an Irish ballot paper
is reproduced below.
How politicians are elected
To get elected a candidate must receive enough votes to reach or exceed an electoral
quota (the Droop Quota: which is calculated on the basis of the number of valid votes
and the number of seats in the constituency). The election count occurs in a number
of stages. While this is quite complex, it is not necessary for the voter to understand
how the counting works in order to vote effectively. First, the returning officer orders
the ballot papers in terms of the Number One votes marked against every candidate. If
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For example if a party gets 10% of the vote in a constituency, giving the party 10% of the
seats will be impossible in a five seat constituency but easily done where the constituency has
ten seats.
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any candidates reach or exceed the quota at this stage, they are deemed elected. What
follows then is a series of count stages that can be either one of the following:
 A transfer of the surplus votes (i.e. those votes that exceed the quota) of
elected candidates to the remaining candidates based on the next preference
indicated on each ballot paper;
 Or in the event that there are no surplus votes to transfer, the returning officer
eliminates from the count the candidate with the lowest number of votes, and
transfers all of his/her ballot papers based on the next preference indicated on
each ballot paper.
These counting stages continue until the required number of candidates (3, 4 or 5
depending on the size of the constituency in Ireland) has been elected. The fact that
every preference can count (i.e. not just the Number One votes received by the
candidate, but also the Number Twos, Number Threes and so on) means that
candidates make every effort to attract preference votes from all voters.
Countries using this system
STV is an extremely rare electoral systems used only in Ireland and Malta to elect its
main (lower) house of parliament; though Australia uses it to elect its Senate (upper
house). It is also used at sub-national level for electing regional parliaments in such
places as Australia and Northern Ireland (the Northern Ireland Assembly) and for
local elections for instance in New Zealand and Scotland.
Variations
There are a large number of ways in which STV can vary; here are some of the more
significant forms of variation:
 In Malta and Australia, the constituency sizes are larger, which means that the
election results are more proportional.
 Candidates are not listed alphabetically in Australia (to guard against alphabetical
voting). In both Malta and Australia, candidates are grouped together by their
party affiliation.
 Malta and Australia do not use by-elections to fill vacant seats in parliament.
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An Irish STV ballot paper